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New PS one-turn delay feedbacks
and further developments
Damien Perrelet BE-RF-FB CERN
LIU-DAY 2014, 11 April 2014
Thanks to Alfred Blas, Heiko Damerau, Valentin Desquiens, Simone Gilardoni, Guido Sterbini, Letizia Ventura,
and all involved people from sections BE-RF-FB, IS and CS
Content
Overview of the new feedback board
Current implementations:
- PS 10 MHz 1-turn feedback and AVC digital loops
- PS transverse damper
Future developments:
- PS 1-turn feedback cavities 13/20/40/80 MHz
- PS longitudinal coupled-bunch feedback
- PSB/AD/LEIR transverse damper upgrade
Summary and outlook
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The new hardware
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New PS feedback hardware
4 ADC RF INPUT CHANNELS
LMH6702
Gap Return
LP
→
FPGA
→
4 DAC RF OUTPUT CHANNELS
FPGA Stratix II EPS2S90F1020C4
ADCs AD6645
CLK DWSTR1
ADC1
DACs AD9754
DAC1
G Ctrl
Vprog Test
LP
ADC2
AD8009
LP
Power
Combiner
DAC2
LP
1TFB TP
DRIVE IN
VPROG TP
50 MHz
Clock Distri
h200
BP1
RF from BC
G Ctrl
NODLY
d UPSTR
d nUPSTR
d DWSTR1
d DWSTR2
LP
CLK UPSTR
Digital
G Ctrl
ADC3
DAC3
G Ctrl
Spare
LP
DAC4
ADC4
50 MHz
CLK DWSTR2
AVC TP
LP
Power
Combiner
LP
VGAP DET TP
SRAM
4 SERIAL LINKS
3/21/2014
VME + TRIGGERS
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Electronic board
- Generic VME board
-
STRATIX II FPGA and external SRAM
4 RF channels ADC and DAC, low latency, 14 bits and running at 105/125 MSPS
2 multiplexed fine delay lines for glitch-free delay changes (DAC and FPGA clocking)
4 serial links CVORB or fast 40 Mbit/s
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PS 10 MHz loops
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PS 10 MHz cavity feedback overview
Final amplifier,
2.8-10 MHz cavity,
fast wideband FB
H
Gap
return
Drive
DAC
1TFB
DAC
AVC
hn
3/21/2014
h200
Vprog
- Slow voltage control loop (AVC)
 Gain control at fRF
ADC
Reduction of cavity impedance
seen by the beam:
ADC
- Fast wide-band feedback
around amplifier (internal)
 Gain limited by delay
- 1-turn delay feedback
 High gain at n  frev
RF from BC
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PS 1-turn delay feedback
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1-turn delay feedback
IIR fractional notch hn/hs
Suppress the RF component
to not work against AVC
High gain at frev multiples
DPRAM
FPGA
VGAP
Detected
hn
VPROG
RF CLK
h200
ADC
Cascade of notch + comb
Periodic comb at frev
NOTCH
FILTER
COMB
FILTER
AUTO
DELAY
DAC
1TFB OUT
to Drive
hn
NOTCH BYPASS
d UPSTR
d DWSTR
VME
INTERFACE
Fine delayed clock
Unique sampling clock h200 integer multiple of the revolution frequency
8/4/2014
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Measurements with beam before LS1
Spectrum at cavity
gap voltage of a single high
intensity bunch 8∙1012 ppb
h=8
Beam induced spectrum of four
bunches during batch compression
10 db/div
FB off
time
Filters only and closed loop
transfer functions
h = 8  13  20
FB on
frequency
3/21/2014
Feedback
succesfully
follows
harmonic
changes
time
amplitude
10 db/div
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frequency
10
PS digital AVC loop
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AVC loop and AVC surveillance
RF from
beam control
Collaboration
RF-FB
RF-IS
ADC
RF veto
Voltage
program +
Error[k]
-
PID
controller
DAC
Drive
Modulator
Detected
gap voltage
Power
amplifiers
hn
I
CORDIC
Q
non-IQ
detection
ADC
Gap
return
Cavity
10MHz
 Amplitude loop only, future phase loop or move to IQ loop
 Voltage detection using non-IQ algorithm at given harmonic hn
H. Damerau, V. Desquiens,
 High power hardware safety ensured by separate surveillance module M. Haase, D. Perrelet
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Digital AVC loop measurement
• Step response of the controller around a cable
500 ms test pulse voltage program
Response with fast voltage rise
Vprog
Vprog
Vdet
Error
RF drive
Vdet
15 turns
Error
Error
100 ms/div
RF drive
10 ms/div
 Digital PID with adjustable parameters
 Regulation to full voltage without overshoot in about 15 turns
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Installation in the machine
Four new VME crates installed in building 359 (one for each tuning group)
Example for tuning group B (cavities C56, C66, C76 and C81)
 Full commissioning of the new system during start-up 2014
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PS transverse damper
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PS transverse feedback
Firmware: A. Blas
1)
2)
3)
4)
3/21/2014
PU flight time compensation
Periodic notch filter for orbit offset suppression
Hilbert filter for phase compensation at betatron frequencies
Automatic delay to complete 1 turn
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PS transverse feedback
See talk by Raymond Wasef
Damper to cure horizontal and vertical transverse instabilities
Damping of head-tail instability
Damping of injection errors
FB OFF
FB ON
X position [a.u.]
1
0.5
0
10 ns/div
10 ns/div
−0.5
−1
2
2.5
3
t [ms]
3.5
PS TFB OFF
PS TFB ON
→ Present PS TFB designed to damp 44 μm/turn at 1.4 GeV (BW 23 MHz).
A.Blas, S.Gilardoni, G.Sterbini
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New applications
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PS 1-turn feedbacks cavities 13/20/40/80 MHz
Frequency conversion board
1) Analog conversion to IF and IQ digital processing
→ Using existing and analog frequency conversion boards
or
Thomas Truszczyński
2) Direct sampling
→ Modification of existing board
to achieve higher sampling capabilities
Mini-PCB to fast ADC adaptation
or
→ Build a complete similar new and fast board
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PS longitudinal coupled-bunch feedback
See talk by Letizia Ventura
Cross-damping: hdet + hkick = hRF = 21 → Detect at h = 13 and Damp at h = 8
→ Make a new digital coupled-bunch feedback for the Finemet cavity
Beam
(WCM)
ADC
DAC
Longitudinal
kicker (Finemet)
H. Damerau, L. Ventura:
•
Demonstrated with measurements using existing feedback and the spare cavity
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Future developments
Target to other machines:
- Upgrade of PSB, AD and LEIR transverse dampers
PS 10 MHz possible improvements:
- Cavity phase loop or IQ loop (Reliability of RF manipulations)
- Cavity phase compensation (More gain for 1-turn feedback)
- Multi-harmonic RF generation on-board and use of hs=256
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Summary and outlook
- New generic feedback board meets requirements
→ Complex design but easy to use and allows lots of features
- Two operational loops: PS 10 MHz 1-turn feedback and AVC
→ Fully digital and remote controlled
→ Commissioning during setting-up 2014
- New operational PS transverse damper
→ Good results and required for LIU beams
- Many future developments and projects using this hardware
→ FPGA gives reliability and flexibility for new ideas
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Thanks for your attention
Many thanks to people from sections RF/FB-CS and RF/FB/IS for collaboration and support :
Alfred Blas, Philippe Baudrenghien, Andy Butterworth, Heiko Damerau, Valentin Desquiens,
Simone Gilardoni, Gregoire Hagmann, Matthias Haase, Wolfgang Hofle, Michael Jaussi,
Gerd Kotzian, Tom Levens, Gérard Lobeau, John Molendijk, José Noirjean,
Anthony Rey, Maarten Schokker, Guido Sterbini and Letizia Ventura.
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